Insulator



April 16, 1935. M, w s 1,997,666

INSULATOR Filed May 3, 1933 WIT-NESSES:

44 INVENTOR George fl7. 14/ z'sler.

4 l w A: I I If BY L 24 Patented Apr. 16, 1935 INSULATOR George M. Whisler, Berkeley, Calif., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 3, 1933, Serial No. 669,169

4 Claims. (Cl. 173-318) My invention relates to transmission line insulators and it is an object thereof to provide an insulator of improved design wherein the eifect of corona discharge and attendant interference with radio reception is minimized.

In transmission line insulators, particularly when used in conjunction with high tension lines or apparatus, the development of corona discharge has an undesirable effect on radio reception. Such effect is well known and many expedients have been proposed to eliminate it. According to the present invention, a conducting film or coating is disposed on a surface or surfaces of the insulator, where corona discharge is apt to occur, in such manner that the discharge occurs at the peripheral edge of the film or coating and is directed away from the porcelain surface of the insulator.

In the accompanying drawing:

Figure 1 is a view in elevation, partly in section, of an insulator embodying my invention; and

Fig. 2 is a view in vertical section, of a modification of a portion of the construction shown in Fig. 1.

Referring to the drawing, there is shown a multi-shed pin-type insulator of porcelain or other suitable dielectric material (Fig. 1) having an upper section I and lower sections 2 and 3 in interfitting nested relation. Each section is provided with a usual outstanding flange 4, 5 and 6, respectively, and the upper section l is provided with a depending flange I in accordance with usual practice.

The upper portion i has an enlarged head 8 adapted to receive a metallic cap 9 which, in turn, is designed to support the transmission line or electrical apparatus.

In accordance with usual practice, layers or portions of resilient material in, such as asphaltum, are disposed between the cap 9 and the cylindrical head portion 8, and between corresponding portions of the nested sections. These are-for the purpose of relieving the mechanical stresses set up by unequal expansion between the various parts and to provide a resilient bearing medium for cushioning the load imposed on the cap 9.

The cup-shaped recess in the lower. unit 3 is proportioned to receive a metallic supporting pin l2 which is provided, in a usual manner, with discontinuous horizontal flanges or ridges l3, and vertical flanges or ridges l4.

A suitable sealing compound l5, such as cement, is disposed between the head of the pin 12 and the walls of the recess inthe lower member 3, as well as the space between the nested portions of the units l, 2 and 3, and between the cap 9 and the head 8 of the upper portion l.

The construction thus far described is in accordance with present and usual practice in the construction of multi-part insulators.

The upper surface of the upper unit I is provided with a shoulder [6 which is circular in horizontal contour and the plane thereof is above and angularly related with respect to the remainder of the creepage surface.

A conducting film or coating l8 which may be a metallic glaze as disclosed in Patent No. 1,852,093, Smete et al, dated April 5, 1932, or other suitable metallic or semi-conducting coating which may be applied by a spraying orglazing operation, entirely covers the shoulder I6 and extends up the side of the head portion 8 a sufiicient distance to effect an electrical connection with the metallic cap 9. The corona discharge which would normally occur between the lower lip of the cap 9 and the adjacent porcelain surface is accordingly transferred to the peripheral edge of the coating and will be directed outwardly into the air, and in view of the angular relation between the plane of the shoulder l6 and hence the coating l8, and the plane of the uncoated portion of the creepage flange 4, the corona discharge will not tend to creep along or follow the contour of the creepage flange.

Similarly, the portions 2 and 3 are provided with shoulders I9, 20 and 2! which have'coatings 22, 23 and 24, respectively, disposed thereon to direct corona discharge, which normally would occur at the cemented joints, to take place in the surrounding air. As in the case of the upper section I, the plane of the film bands with relation to the plane of the unfilmed portion is such that the corona discharge cannot follow the creepage flange surface. It will be noted that the upper edge of the coatings 22, 23 and 24 are in contact with and covered by the cement in the respective joints, and it may be desirable to fill the gap between the lower lip of an enveloping shell and the coating below it on an enveloped shell with cement (as shown at 30 and 3| in Fig. 2) to cause the flow of stress through the porcelain body of the insulator.

Although I have shown, as a specific embodiment of my invention, an insulator of the pin or pedestal type, quite obviously the invention is applicable to all insulators having a surface or surfaces subject to corona discharge of a character wmch is apt to cause interference with radio reception, and, although I'have shown an insulator of the multi-shed type, quite obviously the invention is applicable to insulators having only a single shed or creepage surface.

Quite obviously various modifications may be made within the scope of my invention, and it is my intention that no restrictions should be placed thereon, except as imposed by the prior art and set forth in the appended claims.

I claim as my invention:

i. In an insulator, a body of dielectric material comprising a substantially cylindrical raised central portion, a metallic cap disposed on said central portion, a laterally extending creepage flange surrounding said central portion and having an annular raised shoulder thereon, and an electrically conducting coating covering said shoulder and a portion of said raised central portion; the plane defined by the coated shoulder being so related to the plane of the uncoated portion of the creepage flange that corona discharge from the edge of the coating will be directed away from the uncoated portion.

2. In an insulator, a body portion of dielectric material having a laterally extending creepage surface, and a conducting coating covering a por-. tion of said surface; said creepage surface being so formed that the angular relation between the planes formed by said coated and uncoated pormenace tions is such that corona discharge from the perimeter of the coating will be directed away from the uncoatedportion.

3. In an insulator comprising a plurality of nested body portions of insulating material having laterally extending creepage flanges thereon,

,a metallic cap on the upper of said body portions, a metallic pin disposed in a recess in-the lower'of said portions in supporting relation, and means for maintaining said cap, body portions and pin in nested operative relation; an annular shoulder formed on the surface of said upper body'portion surrounding said cap and defining a plane angularly related to the plane defined by the remainder of the upper surface, and a coating of electrically conducting material disposed on said shoulder in electrical contact with :the periphery of said cap. 

